Numerous four-way valve assemblies have been developed for controlling both liquids and gases, and such assemblies incorporate a wide range of structural and functional features. Such four-way valve assemblies have, for many years, been of substantial size and have often incorporated multiple shiftable valves in order to provide for proper control over fluid flow. Modern technology, however, has increasingly demanded that such valve assemblies be made of extremely small size, particularly for use in control circuits. such assemblies must also permit shifting of the valve with extremely small force without detracting from the desired response time.
One of the common problems associated with many known four-way valves, particularly when they utilize shiftable valves of the poppet type, has been the fact that such assemblies often require at least two poppet-type shiftable valve stems in order to provide the desired structural and functional relationships. This increases the structural complexity of the valve assembly, including both the size and functional characteristics, and also significantly increases the manufacturing cost. The use of multiple valve stems also increases the number of wear points subject to failure and/or maintenance.
A further problem associated with known valve assemblies, particularly in those assemblies which are of extremely small size so as to be suitable for use in control systems, is the difficulty in maintaining proper tolerances including concentric relationships between the shiftable valve stem and the housing so as to permit optimum performance including minimization of shifting force. This precision of manufacture has often been compromised in view of difficulties in achieving such manufacture, or at least the impracticality of doing so at reasonable cost.
To improve upon many of the aforementioned disadvantages, the Assignee's copending application Ser. No. 158 084 illustrates an improved single-stem four-way valve employing a single solenoid actuator for the stem, coupled with a spring return. The valve assembly of this copending application is particularly desirable in view of the manner in which the valve stem is supported on lines which function to permit proper alignment of the housing end parts relative to the center housing part to achieve precise tolerance and dimensional control so as to permit minimization of parts and minimization of shifting forces. In this valve assembly, however, since the valve stem is slidably guided on the housing end parts, which in turn are aligned by the liners relative to the center housing part, the valve stem is preferably constructed of brass or similar material so as to be properly slidably disposed for direct engagement with the housing end parts (which are of steel). Constructing the stem of brass or similar soft material, however, creates a wear problem on the end of the stem due to contact by the solenoid plunger.
Accordingly, it is an object of the present invention to provide an improved four-way valve assembly employing a single stem actuated at opposite ends by opposed solenoids, which improved valve assembly incorporates an improved slidable support for the stem so as to permit constructions of the stem from steel or other suitable hard material while avoiding direct slidable support of the stem on the housing, while at the same time maintaining precise tolerance and dimensional control.
It is also an object of the invention to provide an improved valve assembly, as aforesaid, which slidably pilots the stem directly on liners which can be constructed of brass or similar material, with the liners in turn being stationarily supported on the housing.
It is a further object of the invention to provide an improved valve assembly, as aforesaid, which preferably employs a shiftable valve stem which is basically of the poppet type for controlling flow from an inlet port to a pair of load ports, with the poppet valve incorporating a detent function to assist in positively holding the valve in its selected position.
In the improved four-way valve assembly of the present invention, and specifically in the preferred embodiment thereof, there is provided a housing having an elongate bore in which is slidably disposed a single shiftable valve of the poppet type. A pair of sleevelike liners are stationarily disposed in the bore and cooperate with the housing for defining an inlet port which communicates with the bore in the region between the adjacent ends of the lines. A pair of load ports communicate with the bore through the individual liners and are spaced axially on opposite sides of the inlet port. A pair of exhaust ports communicate with the bore adjacent the opposite ends thereof. A single valve has a poppet mounted centrally thereof and disposed so as to axially shift between and sealingly coact with valve seats formed on the opposed inner ends of the liners. These latter valve seats are preferably formed as shallow recesses which create a slight elastomeric compression of the poppet valve. The single shiftable valve has the stem thereof preferably constructed of steel, and the opposite free ends of this stem are slidably supported on and project through seal rings mounted adjacent the opposite ends of the housing in the vicinity of the exhaust ports. The opposite ends of the stem are disposed directly adjacent and engaged by opposed ends of solenoid plungers for effecting shifting of the valve for flow selection purposes.
Other objects and purposes of the invention will be apparent to persons familiar with structures of this type upon reading the following specification and inspecting the accompanying drawings.